It is known in the art to track movement and locations of items using human involvement, such as reading barcodes, or without human involvement, such as automatically detecting items that pass through a field such as an antenna. For example, US20050258956 discloses an RFID reader detecting a tag's emitted RF signal when the signal is within the range of the reader's emitted RF field. The reader detects the presence of an RFID tag by detecting its RF signal, and processes the received RF signal to accurately determine the unique identification code of the tag. However, such a conventional system only determines where an item has previously passed through and cannot determine where an item is currently.
Some conventional systems employ beacon transponders on the item to be tracked. These systems are capable of determining actual location of the item; however, the beacon transponders require substantial power consumption. These systems require a vast and costly installation of antennae and/or infrared (IR) detectors in a facility. The beacon transponders are costly and require considerable maintenance to replace the batteries, assuming the transponders can be located after the batteries die.